The work aims to design tubular side-folding bag-opening mechanism for prefabricated bags so as to avoid falling during the filling by bag-delivering machine for dried noodles. According to filling technology of dried noodles and bag delivering process, the rocker-slider bag-opening mechanism was designed. The constraint equation method was used to establish the model to design the bag-opening mechanism, and the kinematics analysis of the rocker-slider mechanism was carried out by assur-group method. Matlab programming was applied to solve the dimensional parameters and kinematic parameters of the rocker-slider mechanism, and the angular displacement, angular velocity and angular acceleration curve of the rocker were drawn. Based on this design, the bag-opening mechanism was processed and tested online and the reliability was also verified. The parameters of the rocker-slider mechanism were as follows: link length of 89 mm, rocker length of 115 mm, offset distance of 122.5 mm, driving link slider travel of 10 mm, and driven link rocker sway of 5°. The displacement of the slider and the angular displacement of the rocker satisfied a linear relationship. The angular acceleration of swing link was approximately uniform. Through online test, the bag-opening mechanism meets the technological requirements and the reliability of bag-opening mechanism reaches 94.6%, thus meeting the requirements on automatic bag-delivering machine for dried noodles by enterprises and solving the falling of dried noodle packages better.